Encorochment of property without proper documents

Sir my mother is having shop in her name in new Delhi at Palam n I m having a brother who was in heavy debt because of improper financial planning and shortcuts to earn more he was residing with mother back at Delhi m in defence service posted presently at Bangalore.My brother insist my mom to sell the shop which was on her name to clear his debt to which she agreed but with certain set of conditions that he will register the property to he seller name only once she will be back from Bangalore that is my home as I had called her to Bangalore to help me as my wife was in her advance stage of pregnancy meanwhile she had taken the token amount from the purchaser and and she put a condition that registry will only be done once she is back from Bangalore but against it the purchaser has given the complete amount to my brother who was already in debt such is claimed by the purchaser once my mom was back from Bangalore she came to know bout encroachment and the series of legal notice began meanwhile my mom thrown out my same brother from home now sir wat my mother shall do she is illiterate and all alone there. Presently she said she has receive summon from dwarka court please help me legally.